Process for the preparation of the esters of unsaturated acids



Patented Nov. 12, 1935 PROCESS FOR THE PREPARATION OF THE ESTERS OF UNSATURATED ACIDS Emmette F. Izard, Elsmere, Del., assignor to E. I. du Pont de Nemours 8; Company, Wilmington, Del.,a corporation of Delaware No Drawing. Application October 21, 1933,

Serial No, 694,641

15 Olaimsi (Cl. 260-106) a new and improved process for the preparation (3) CH 3-CCOOCH3+HC1. I

By the substitution of other monoor polyhyized by those skilled in the art that a plurality of the esters of the unsaturated aliphatic organic acids. Another object of the invention is to provide a process for the preparation of acrylic acid esters from 'chlorformic esters and ethylene. A further object of the invention is to provide a new and improved process for the preparation of the methyl ester of methacrylic acid. Another object of the invention is to provide a process for the preparation of the methyl'ester of methacrylic acid including the preparation of the chloriormate and propylene. A still further obacrylic acid. Other objects and advantages will hereinafter appear.

According to the present invention an ester of the unsaturated monocarboxylic aliphatic organic acids may be obtained in the following manner. Phosgene, or other carbonyl halide, is reacted with an aliphatic monohydroxy or polyhydroxy alcohol to form the alkyl ester of chlorformic acid; other suitable methods for making these esters may be employed. Thus, from methanol, methyl chloriormate is obtained; from ethanol, ethyl chloriormate; from glycerine, glycerol chlorformate, and like esters are obtained from the higher alcohols. The alkyl ester is then added to an oleflnic hydrocarbon, such as ethylene, propylene, butylene, etc. to obtain the ester of a halogenated aliphatic carboxylic acid which is dehydrohalogenated to give an unsaturated aliphatic ester. The preparation of methyl methacrylate from phosgene, methanol, and propylene, when conducted in accord with my invention, will proceed substantially in accord with the equations:

(methylchlorformate) 80 and/or methyl ester of chlorisobutyric acid from methyl ated ester to give the methyl ester of methylof unsaturated esters suitable as plasticizing agents, for use in the preparation of synthetic resins, as solvents, etc. may be obtained. From 10 ethanol, methoxy ethanol, propanol, cyclohexanol, glycerol, etc. with phosgene and ethylene will be obtained, for example, respectively, ethyl, methoxy-ethyl, propyl, cyclohexyl and glyceryl acrylates, and with propylene, butylene, styrene, 15 in lieu of ethylene, will be obtained thecorresponding methacrylates', propacrylates, and phenacrylates.

Altho I usually prefer to obtain the alkyl chlorformate by the interaction ofphosgene with alcohol, it may be prepared by the halogenation of an alkyl formate. The product designated under (3) above is, of course, not the sole product of the reaction; for example, under some conditions methyl crotonate is obtained as a result of the 95 formation in reaction (2) of themethyl ester of. betachlor-normal-butyric acid. It will be readily appreciated by those skilled in this art that by substituting an appropriate alpha beta unsatu- 0 rated hydrocarbon for propylene acrylic acid derivatives can be obtained containing practically any desired group in the alpha position.

I shall now describe examples illustrating methods of conducting my process, but it will be r understood that the details therein given will in no way limit the scope of my invention.

Example 1.--.Methanol is mixed at room temperature and pressure with phosgen'e in an autoclave until approximately kilograms of phos- 40 gene have been absorbed by approximately 10 liters of methanol; the temperature is then raised to approximately C. and'after substantially all of the hydrogen chloride has passed on aluminum chloride is added to give a solution containing 5-15% of aluminum chloride. Propylene is then introduced under a pressure of approximately 50 atmospheres, which pressure is. maintained in the autoclave. Alcoholic'caustic soda of approximately 10% strength is added 50 after the reaction has proceeded to substantial completion and the methyl methacrylate obtained is separated and purified by known methods. I

Example 2.-In lieu of introducing propylene as directed in Example 1, ethylene isintroduced under a pressure of approximately 50- atmospheres. The methyl ester of acrylic acid is obtained and may be separated from the reaction products in the mannerdisclosed in the first example.

The condensation of the alkyl or aryl chlorformate with the olefinic hydrocarbon may be conducted at a temperature of from -150 C. or higher and at a pressure of from 1-100 atmospheres.

A number of catalysts may be employed. in these reactions, such, for example, as the chlorides of aluminum, iron, bismuth, boron, or corresponding bromides and equivalent condensation catalysts, promoted or unpromoted activated charcoal are also suitable. In many instances also these same catalysts may be used in the dehydrohalogenation of the halogenated esters of the saturated acids to the alkyl ester of the unsaturated acid, altho the caustic method is preferable. The catalyst, therefore, need not, in certion it will be realized that any modifications or improvements in the process hereinbefore described will come within the scope of the invention without sacrificing any of its advantages.

I claim:

1. A process for the preparation of an ester of an unsaturated aliphatic carboxylic acid which comprises reacting the ester of a halogenated formic acid with an oleflnic hydrocarbon, and dehydrohalogenating the resulting ester. of a halogenated saturated aliphatic monocarboxylic acid to an unsaturated ester.

2. A process for the preparation of an ester of an unsaturated aliphatic carboxylic acid which comprises reacting the ester of a halogenated formic acid with ethylene, and dehydrohalogenating the resulting ester of a halogenated propionic acid to an unsaturated ester.

.3. A process for the preparation of an ester of. an unsaturated aliphatic carboxylic acid which comprises reacting the ester of a halogenatedformic acid with propylenefand dehydrohalogensting the resulting ester. of a halogenated isobutyric acid to an unsaturated ester.

4. A process for the preparation of an ester of methylacrylic acid which comprisespreparingan ester of chlorformic acid by reacting phosgene with an alcohol, effecting an addition reaction between this ester and propylene, thereby obtaining the ester of betachlorisobutyric acid, and

tion between thisester and propylene, thereby obtaining the alkyl ester of betachlorisobutyric acid, and finally dehydrohalogenating this ester to obtain an alkyl ester of methylacryiic acid.

6. A process for the preparation of an ester of methylacrylic acid which comprises preparing a hydroaryl chlorformate by reacting phosgene with a cyclohexanol, eii'ecting an addition reaction between this ester and propylene,'thereby obtaining the hydroaryl ester of betachlorlsobutyric acid, and finally dehy thisl ester to obtain an aryl ester of methylacrylic g aci 7. A process for the preparation of the methyl ester or methylacrylic acid which comprises preparing methylchlorfomate by reacting with methanol, eflecting an addition reaction bem tween methyl chlorformate and propylene, thereby obtaining the methyl ester of betachlorisobutyric acid, and finally dehydrohaiogenating the methyl ester of betachlorisobutyric acid to obtain methyl methacrylate.

8. In a process for the preparation of an star of an unsaturated aliphatic monocarbonlic acid. the step which comprises reacting a halogenated formic ester with an olefinic hydrocarbm. v

9. In a process for the preparation of an alkyl 39 ester of acrylic acid, the stepwhich eomprilu reacting an alkyl halogenated formate with ethylene.

10. In a process for the preparation of an akyl ester of methacrylic' acid, the step which com- 5 prises reacting an alkyl halogenated formate with propylene.

11. In a process for the preparation of the methyl ester of methaerylic acid, the step which comprises reacting methyl chlorformate with go propylene.

12. In the process for the preparation of the methyl ester of methacrylic'acid, the step which comprises reacting methyl chlorformate with propylene in the presence of a catalyst selected 35 from the group consisting of a chloride of iron, bismuth, aluminum, and boron. 13. A process for the preparation or an ester of an unsaturated aliphatic carbonlie acid which comprises reacting the ester or a halogenated 40 formic acid with an olefinic hydrocarbon in the presence of a. metal halide catalyst, and dehydrohalogenating the resulting ester of the halogenated saturated aliphatic monocarboxylic acid to an unsaturated ester. 45

14. A process for the preparation of the methyl ester of methacrylic 'acidwhich comprises pmparing methyl chlorformate by reacting phoqene with methanol, condensing the methylv chlorformate with propylene in the presence of a 50 metal halide catalyst, thereby obtaining the methyl ester of betachlorisohutyric acid, and finally dehydrohalogenating the methyl ester of betachlorisobutyric acid to obtain methyl methacrylate.

15. A process for the preparation of an ester of an unsaturated aliphatic carboxylic acid which comprises reacting the ester of a halogenated formic acid with an olefinichydrocarbon in the presence of a condensation catalyst and dehyw drohalogenating the resulting ester of the halogenated saturated aliphatic molic I acid to an unsaturated ester.

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